We recently received a tech question from one of our readers, which I felt should be addressed by someone who is considered one of the best Harley-Davidson technicians in the Midwest, 'Dyno' Mike Wilson of Dyno Mike's Dynamic Chassis.
Question: Lately there has been a lot of press about late model Twin Cam tensioner wear and failure. I ride a 2002 Dyna FXDX with 37K miles on her. Most of the mileage I have acquired is highway miles (85%). My friend Dave has a 2001 Road King with 30K miles on her and had a recent service done to his bike and had the Twin Cam cover opened and had the tensioner examined. The service department had given him a positive feedback, stating that his tensioners were fine and there was no sign of wear. His bike like mine has stage 1, with no engine mods. The articles and news release I had read lately had most of the Twin Cam tensioner failure from southern states (Arizona, Florida, California) with stage 1 and engine mods. I donít know, but I think that this cam tensioner failure and wear has to do with climate, modification, and service. I myself use Syn tech 3 H-D oil since my 1K break in. I would appreciate feedback on this issue for Twin Cam owners that have over 25K miles on their machines. I feel that these articles are not noteworthy, because the issue at hand is not researched enough. Sure there are many variables involved; however, I think that they should not scare the many Twin Cam owners because a small percentage of these late models are having problems. Moreover, they blame H-D for poor design for these factory tensioner and promoting aftermarket replacement products. The way I see it, H-D had spent millions in the development and research with the Twin Cam motor (FATHEAD) that I have confidence that this is isolated issues. Lastly, with my experience, I have had no problems with the current crop of H-D machines that we had purchased in Ď01 and Ď02. Both bikes are running good, and I keep a strict maintained schedule on both my machines.
Dyno Mike: This is a very commonly asked question and a big concern of all the Twin Cam owners. Being in the performance field for over 10 years I have personally looked inside hundreds of Twin Cam motors and have seen first hand a variety of wear patterns on several internal parts.
First, the Twin Cam had the problem with the cam chain gear sprocket bolts, which was actually more of a key way problem in the gear itself. I saw several that failed when the bolt was still intact. The key in the big gear only had about 20 percent engagement in the shaft. Harley finally did away with this design and replaced it with a splinted shaft and gear, which solved this problem.
Next, was the B motors and the threat of the balancers being over-revved. I personally saw only one motor failure from this and the problem existed only because the shaft that turned the balancing weight chain gears only engaged about halfway through the drive gear. This was caught and redesigned halfway through the production year in 2000. Iím not sure that 7000 RPM ignition modules are that harmful to the B motors especially if you realize that lots of metric bikes have balancing weights that turn in excess of 11,000 RPMs. All the motors I build have a 7000-RPM limit in the A and B motors. I stand behind the motor for one full year regardless of mileage. For example, I shift my 103 cubic inch B motor in my Fat Boy at 7500.
Next came the chain tensioner issue, and this is why I donĎt worry about mileage. Iíve seen motors with 2000 miles on them with two broken or worn tensioners. Iíve also seen motors with 75K on them with virtually no wear whatsoever on the tensioners. From what I have experienced, the way you ride or what oil you use doesnít necessarily have anything to do with wear on the tensioners.
One possibility could be on how the cam chain itself is worn. Let me explain what I meant by that statement. The pitch on the cam gears can vary from bike to bike or more so cam to cam. When the gear pitch varies the cam chain will wear prematurely and can cause the chain to develop burns and cause the chain to stiffen up. This can eat into the soft phenolic cam chain tensioner shoes like a chain saw. I would highly recommend replacing the cam chain if you experience any wear on the tensioner itself.
Another thing you should do is inspect the oil pump for scratches on the return side of the pump, because once you have any wear on the internal engine components the oil pump on the Twin Cams can really suffer. Remember the Harley motors are really dry sump motors like what racecars have. The oil is held in a remote location, and if the pump gets worn or has any scratches in the return side, the motor will retain oil and cause rapid power loss. I recommend checking the cam chain tensioners every 10,000 miles.
If you have questions or need any further assistance with this problem, feel free to call Dyno Mike Wilson at (816) 322-0379 or e-mail him at firstname.lastname@example.org.
Mike and I agree that preventative maintenance is not only a good idea but also a safe and smart way to take care of your motorcycle.
B-safe out there!